Analysis Of Wrinkling And Tearing Behaviors Of Membrane With Incisions

Due to its excellent quality,small size and easy folding,membrane structures are widely used in aeronautic and aerospace engineering such as solar sails,airships,highaltitude balloon and inflatable wings.However,since membrane is flexible,its bending rigidity is relatively small.When an external force is penetrated or the flexible structure is in long-term service state,an initial micro-crack defect is introduced on the surface of the membrane structure,and then the structure is stretched under the action of an external force.Tearing damage,which affects the bearing performance of the structure.The size,direction and form of the crack have a certain influence on the tensile wrinkling of the membrane structure.Therefore,it is of great significance to study the tensile wrinkling and tearing behaviors of membrane structures under different incision forms.Firstly,through the uniaxial tensile test of polyimide membrane,several marked stages of the membrane wrinkling process were given,and the mechanical properties were tested and analyzed.The displacement-load and stress-strain curves of the membranes under unidirectional loading with a tensile rate of 5 mm/min were obtained.The strain relationship curves and the post-wrinkling morphology and displacement cloud map of the wrinkle stability stage were obtained by VIC-3D non-contact digital image correlation measurement technology.The effect of folding on the mechanical properties of membranes were analyzed and compared with the pure membrane case.On the basis of the experiment,the numerical simulations under the same loading conditions were carried out,and the accuracy of the numerical simulation in analyzing the problem was verified by comparing the experiment with the simulation.Secondly,the tensile tearing behaviors of membrane which has a circular hole in the center of membrane were discussed.It was concluded that the tearing mode of the membrane were the combination mode of open-type and tear-open type cracks,and the membrane is out-of-plane warped at the crack.At the same time,the effects of the length of the incision,the angle of the incision and the shapes of the incision(V-type,W-type,Z-type,X-type and cross-type)on the tensile wrinkling and tearing properties of the membrane were investigated and compared with the pure membrane.The concepts of notch ratio,relative rupture strength,relative elongation,crack growth ratio,etc.were defined,and the effects of different crack lengths and different slit angles on the tensile fracture parameters of the membrane were discussed.The VIC-3D non-contact digital image correlation measurement technology was used to monitor and analyze the tensile wrinkling and fracture process of the membrane with different incision lengths,and the center contained a slit.The wrinkle morphology and displacement evolution process of the slit membrane in the uniaxial tension state were captured by the VIC-3D.Then,the influence of different incisions on the wrinkling performance of the membrane was studied.Through the analysis of a single circular hole in the center of the membrane,the tensile wrinkle mode of the membrane with a center hole defect was obtained.The characteristics of wrinkle morphology and displacement change during the stretching process were taken out by VIC-3D.At the same time,the finite element model of modeling tensile wrinkling behaviors for membrane was established.The influence of the position of the circular hole on the tensile wrinkle of the membrane is discussed by numerical simulation.The modeling results had a good agreement with the experimental results.The availability of finite element model was verified.The results showed that the shape of the incision and the position of the incisions had a great influence on the wrinkle behaviors of the membrane,which has certain reference significance for knowing the control of wrinkles and eliminating wrinkles.Finally,the mechanical response characteristics of the membrane under biaxial tensile stress were studied.The pure membrane,the crack membrane with a slit,the membrane with a crossing slit and the central circular hole membrane were used as the research objects.The membrane wrinkling behavior under the biaxial tension state was studied.The results showed that the biaxial tensile properties of the membrane were affected by the load conditions.